Non-yellowing coating composition based on a hydroxy component and an anhydride component and utilization in a process of coating

Abstract

Disclosed is a non-yellowing coating composition comprising: a hydroxy component having at least two free hydroxyl groups per molecule, and an anhydride component having at least two carboxylic acid anhydride groups per molecule. The anhydride component is derived from a mixture of monomers comprising greater than or equal to 11 percent by weight of an ethylenically unsaturated carboxylic acid anhydride, the balance of the mixture comprised of at least one vinyl comonomer. The molar ratio of the vinyl comonomer to the carboxylic acid anhydride in the mixture should be at least 1.0:1.0 and the ratio should be sufficient to provide a color standard number of less than 150. Typically, the coating composition is in the form of a two-package composition. Also disclosed is a method of coating comprising: (I) coating a substrate with one or more applications of a pigmented basecoating composition to form a basecoat, and (II) coating the basecoat with one or more applications of a transparent topcoating composition to form a transparent topcoat, in which the basecoating composition and/or the topcoating composition comprises the aforesaid non-yellowing coating composition.

What is claimed is: 
     
       1. A non-yellowing coating composition comprising: (A) a hydroxy component having at least two free hydroxy groups per molecule; and   (B) an anhydride component having at least two carboxylic acid anhydride groups per molecule derived from a mixture of monomers comprising greater than or equal to 11 percent by weight of an ethylenically unsaturated carboxylic acid anhydride the balance of said mixture comprisied of at least one vinyl comonomer, the molar ratio of said vinyl comonomer to said carboxylic acid anhydride being at least 1:0:1.0 and sufficient to provide a color standard number of less than 150 f according to ANSI/ASTI test method D 1209-69 when an amout of component (B) sufficient to provide 27 grams of solids of said component is mixed with 1.0 gram of dimethylcocoamine and reduced with butyl acetate to a solids content of 22.5 percent by weight; wherein the amounts of said hydroxy componnents and said anhydide components in said coating composition provide a ratio of equivalents of hydroxyl groups to equivalents of anhydride groupsp in a range of from 3:1 to 1:3.     
     
     
       2. The coating composition of claim 1 wherein cures to a tack free film at a temperature of less than 75 degrees Celsius within 4 hours. 
     
     
       3. The coating composition of claim 1 which is in the form of a two package composition in which said hydroxy component is in a package separate from said anhydride component. 
     
     
       4. The coating composition of claim 1 which is essentially free of opaque pigments and when applied as a film cures to form a transparent crosslinked coating. 
     
     
       5. The coating composition of claim 1 additionally comprising (C) an effective amount of a catalytic agent for accelerating the curing reaction between hydroxyl groups of component (A) and anhydride groups of component (B). 
     
     
       6. The coating composition of claim 5 wherein said catalytic agent comprises an amino group. 
     
     
       7. The coating composition of claim 1 wherein said hydroxy component is selected from the group consisting of simple diols, triols and higher hydric alcohols; an acrylic polyol; a polyester polyol; a urethane polyol; a polyether polyol; an amide-containing polyol; an epoxy polyol; and a mixture thereof. 
     
     
       8. The coating composition of claim 7 wherein said hydroxy component is a film-forming polymer. 
     
     
       9. The coating composition of claim 8 wherein said film-forming polymer is an acrylic polyol derived from a hydroxyalkyl acrylate and/or a hydroxyalkyl methacrylate. 
     
     
       10. The coating composition of claim 9 wherein said acrylic polyol has a peak molecular weight ranging from about 1000 to about 50000 and said anhydride component is a film-forming polymer having a peak molecular weight ranging from about 1000 to about 50000, said molecular weights being determined by gel permeation chromatography utilizing a polystyrene standard. 
     
     
       11. The coating composition of claim 1 wherein said vinyl monomer comprises styrene. 
     
     
       12. The coating composition of claim 1 wherein the molar ratio of said vinyl comonomer to said carboxylic acid anhydride is at least 1.3:1.0. 
     
     
       13. The coating composition of claim 1 which when applied as a film cures to form a crosslinked coating. 
     
     
       14. A method of coating comprising the steps of: (I) coating a substrate with one or more applications of a pigmented basecoating composition to form a basecoat; and   (II) coating said basecoat with one or more applications of a transparent topcoating composition to form a transparent topcoat; wherein at least one application of said basecoating composition and said topcoating composition is a non-yellowing coating composition comprising (A) a hydroxy component having at least two free hydroxyl groups per molecule; and   (B) an anhydride component having at least two carboxylic acid anhydride groups per molecule derived from a mixture of monomers comprising greater than or equal to 11 percent by weight of an ethylenically unsaturated carboxylic acid anhydride the balance of said mixture comprised of at least one vinyl comonomer, the molar ratio of said vinyl comonomer to said carboxylic acid anhydride being at least 1.0:1.0 and sufficient to provide a color standard number of less than 150 according to ANSI/ASTM test method D 1209-69 when an amount of component (B) sufficient to provide 27 grams of solids of said component is mixed with 1.0 gram of dimethylcocoamine and reduced with butyl acetate to a solids content of 22.5 percent by weight; wherein the amounts of said hydroxy component and said anhydride component in said non-yellowing coating composition provide a ratio of equivalents of hydroxyl groups to equivalents of anhydride groups in a range of from 3:1 to 1:3.       
     
     
       15. The method of claim 14 wherein said transparent topcoating composition comprises said non-yellowing coating composition. 
     
     
       16. The method of claim 14 wherein said basecoat and said topcoat are allowed to dry or cure together on said substrate. 
     
     
       17. The method of claim 14 in which said non-yellowing coating composition is in the form of a two package composition in which said hydroxy component is in a package separate from said anhydride component. 
     
     
       18. The method of claim 14 wherein said non-yellowing coating composition additionally comprises (C) an effective amount of a catalytic agent for accelerating the curing reaction between hydroxyl groups of component (A) and anhydride groups of component (B). 
     
     
       19. The method of claim 17 wherein said catalytic agent comprises an amino group. 
     
     
       20. The method of claim 14 wherein said hydroxy component is selected from the group consisting of simple diols, triols and higher hydric alcohols; an acrylic polyol; a polyester polyol; a urethane polyol; a polyether polyol; an amide-containing polyol; an epoxy polyol; and a mixture thereof. 
     
     
       21. The method of claim 20 wherein said hydroxy component is a film-forming polymer. 
     
     
       22. The method of claim 21 wherein said film-forming polymer is an acrylic polyol derived from a hydroxyalkyl acrylate and/or a hydroxyalkyl methacrylate. 
     
     
       23. The method of claim 22 wherein said acrylic polyol has a peak molecular weight ranging from about 1000 to about 50000 and said second film-forming polymer has a peak molecular weight ranging from about 1000 to about 50000, said molecular weights being determined by gel permeation chromatography utilizing a polystyrene standard. 
     
     
       24. The method of claim 14 wherein said vinyl monomer comprises styrene. 
     
     
       25. The method of claim 14 wherein the molar ratio of said vinyl comonomer to said carboxylic acid anhydride is at least 1.3:1.0.